Essential element

All about the essential nutrients

1. Soil Chemistry, Fertility and Nutrient Management (AGL406) Mr. Rohitashv Nagar Assistant Professor & HOD Department of Agronomy School of Agricultural Sciences Career Point University, Kota (Raj.)

2. Lecture-1 Essential elements

3. Mineral Nutrition The process of absorption, translocation and assimilation of nutrients by the plants is known as mineral nutrition. Essential Elements: Plants need 17 elements for their growth and completion of life cycle. they are: carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulphur , iron, manganese, zinc, copper, boron, molybdenum and chlorine, nickel. In addition, four more elements sodium, cobalt, vanadium and silicon are absorbed by some plants for special purposes.

4. The elements C, H, O are not minerals. The rest of the elements are absorbed from the soil and these are called mineral elements since they are derived from minerals. These mineral elements are mainly absorbed in ionic form and to some extent in non-ionic form.

5. Mineral element Ionic form Non-ionic form Nitrogen (N) NH 4 + , NO 3 - CO(NH 2 ) 2 Phosphorus (P) H 2 PO 4 - , HPO 4 2- Nucleic acid, phytin Potassium ( Kalium -K) K + Calcium (Ca) Ca 2+ Magnesium (Mg) Mg 2+ Sulphur (S) SO 4 2- SO 2 Iron (Fe) Fe 2+ , Fe 3+ FeSO 4 with EDTA Manganese (Mn) Mn 2+ MnSO 4 with EDTA EDTA = Ethylene di -amine tetra acetic acid

6. Mineral element Ionic form Non-ionic form Zinc (Zn) Zn 2+ ZnSO 4 with EDTA Copper (Cu) Cu 2+ CuSO 4 with EDTA Boron (B) H 3 BO 3, H 2 BO 3, HBO 3 Molybdenum (Mo) MoO 4 2- Chlorine ( Cl ) Cl - Cl -

7. Nicholas (1961) proposed the term ‘functional nutrient’ for any mineral element that function in plant metabolism whether or not its action is specific. With this criteria, sodium, cobalt, vanadium and silicon are also considered as functional nutrients in addition to 17 essential elements.

8. Classification of essential elements The essential elements can be classified based on the amount required, their mobility in the plant and soil, their chemical nature and their function inside the plant. Amount of Nutrients: Depending on the quantity of nutrients present in plants, they can be grouped into three: basic nutrients, macronutrients and micronutrients. Basic Nutrients: carbon, hydrogen, oxygen, which constitute 96 % of total dry matter of plants are basic nutrients. Among them, carbon and

9. Oxygen constitute 45 % each. Eg. The total dry matter produced by rice crop in one season is about 12 t/ha. In this 5.4 t is carbon, 5.4 t is oxygen and 0.7 t is hydrogen. b). Macronutrients: the nutrients required in large quantities are known as macronutrients. They are N, P, K, Ca, Mg, and S. Among these, N, P and K are called primary nutrients and Ca, Mg and S are known as secondary nutrients. The latter are known as secondary nutrients as they are inadvertently applied to the soils through N,P and K fertilisers which contain these nutrients.

10. c). Micronutrients : the nutrients which are required in small quantities are known as micronutrients or trace elements . They are Fe, Zn, Cu, B, Mo and Cl, Mo, Ni. These elements are very efficient and minute quantities produce optimum effects. On the other hand, even a slight deficiency or excess is harmful to the plants.

11. 2. Functions in the plant: based on the functions, nutrients are grouped into four: basic structure, energy use, charge balance and enzyme activity. Elements that provide basic structure to the plant- C, H and O . Elements useful in energy storage, transfer and bonding- N, S and P . These are accessory structural elements which are more active and vital for living tissues. Elements necessary for charge balance- K, Ca and Mg . These elements act as regulators and carriers.

12. IV. Elements involved in enzyme activation and electron transport- Fe, Mn, Zn, Cu, B, Mo and Cl. These elements are catalysers and activators.

13. 3. Mobility in the soil: based on the mobility in the soil, the nutrient ions can be grouped as mobile, less mobile and immobile. The mobile nutrients are highly soluble and are not adsorbed on clay complex e.g. NO 3 , SO, BO 3 , Cl, Mn. Less mobile nutrients are also soluble, but they are adsorbed on clay complex and so their mobility is reduced e.g. NH4, K, Ca, Mg, Cu. Immobile nutrients ions are highly reactive and get fixed in the soil. E.g. H 2 PO 4 , HPO 4 , Zn.

14. 3. Mobility in plants: N, P and K are highly mobile. Zn is moderately mobile. S, Fe, Mn, Cu, Mo and Cl are less mobile. Ca and B are immobile.

15. 4. Chemical Nature: the nutrients can be classified into cations and anions and metals and non-metals based on their chemical nature. Cations: K, Ca, Mg, Fe, Mn, Zn, Cu. Anions: NO 3 , SO, H 2, PO 4. Metals : K, Ca, Mg, Fe, Mn, Zn, Cu. Non-metals: N, P, S, B, Mo, Cl.

16. factors affecting nutrient availability to plants External Factors: Oxidation Reduction State of Elements: Many elements in their most oxidized state, in which they occur naturally, are favored in adsorption. However, Fe and Mn are more available in their reduced form. Concentration of the elements: the relative concentration of an element influences the livelihood of absorption. Higher the concentration of a nutrient greater is its availability. Moisture content of the soil: the nutrients are readily taken by the plant when they are present in soil solution. Therefore, soil moisture is an important factor influencing the absorption of nutrients. Water helps in transport of nutrients to the root surface.

17. d. Aeration: For active absorption, energy is necessary which is released during respiration. Better aeration of the soil provides sufficient oxygen for the respiration of roots. e. Temperature: temperature has to be favorable both for root and shoot growth and also for microorganisms to increase nutrient availability. f . pH: Soil reaction is an important external factor influencing absorption through its role in nutrient availability. The pH range where nutrient availability is more are: N-6 to 8, P-6 to 7.5 and beyond 8.5, K-7.5 to 8.5.

18. 2. Internal Factors: Cell Wall: cell wall is differentially permeable and selectively absorbs particular cations and anions. Among the cations anions have competitive advantage. But the three important anions which are taken in large quantities are NO 3, H 2 PO 4, SO 4 Aeration: rapid ion uptake and growth of plants are associated with warm, moist and well aerated soil. Ion accumulation is linked with aerobic metabolism. Type of cells and stage of development: the entry of inorganic materials into xylem occurs at the root tips. The absorption of nutrients is primarily by root hair cells. Each root hair may be effective for absorption just for a few days.

19. d. Transpiration: uptake of nutrients is more under high transpiration rates.

20. Mechanism of absorption Nutrients are absorbed by the plants in two ways: Active Absorption: Absorption of nutrients from soil solution containing low concentration of nutrients compared to plant sap, by expending energy, is called active absorption. Passive absorption: Nutrients enter the plants along with transpiration stream without the use of energy.

21. Transport of Nutrients to Root Surface Two important theories, namely soil solution theory and contact exchange theory explain nutrient availability to plants. 1. Soil solution theory: soil nutrients are dissolved in water and are transported to root surfaces by both mass flow and diffusion. Mass flow is movement of nutrient ions and salts along with moving water. The movement of nutrients reaching the root is thus dependent on the rate of water flow. Diffusion occurs when there is concentration gradient of nutrients between the root surface and surrounding soil solution. The ions move from the region of high concentration to the region of low concentration.

22. 2. Contact Exchange Theory : A close contact between root surface and soil colloids allows a direct exchange of H, released from the plant roots with cations from soil colloids. The importance of contact exchange in nutrient transport is less than with soil solution movement.

23. Criteria of Essentially Arnon and Stout (1939) proposed criteria of essentially which was refined by Arnon (1954). An element is considered as essential, when plants cannot complete vegetative or reproductive stage of life cycle due to its deficiency. When this deficiency can be corrected or prevented only by supplying this element. When the element is directly involved in the metabolism of the plant.

24. Nutrients deficiencies symptoms and function Nitrogen : symbol: N; available to plants as nitrate (NO3–) , and ammonium (NH4 +) ions. functions: • N is biologically combined with C, H, O, and S to create amino acids, which are the building blocks of proteins. Amino acids are used in forming protoplasm, the site for cell division and thus for plant growth and development. • Since all plant enzymes are made of proteins, N is needed for all of the enzymatic reactions in a plant. • N is a major part of the chlorophyll molecule and is therefore necessary for photosynthesis. • N is a necessary component of several vitamins. • N improves the quality and quantity of dry matter in leafy vegetables and protein in grain crops.

25. Deficiency symptoms • Stunted growth may occur because of reduction in cell division. • Pale green to light yellow color (chlorosis) appearing first on older leaves, usually starting at the tips. This is caused by the translocation of N from the older to the younger tissues. • Reduced N lowers the protein content of seeds and vegetative parts. In severe cases, flowering is greatly reduced. • N deficiency causes early maturity in some crops, which results in a significant reduction in yield and quality.

26. Phosphorus : S ymbol : P; available to plants as orthophosphate ions H 2 PO 4 - , HPO 4 2- . functions • In photosynthesis and respiration, P plays a major role in energy storage and transfer as ADP and ATP. • P is part of the RNA and DNA structures, which are the major components of genetic information. • Seeds have the highest concentration of P in a mature plant, and P is required in large quantities in young cells, such as shoots and root tips, where metabolism is high and cell division is rapid. • P play major role in root development, flower initiation, and seed and fruit development.

27. Deficiency symptoms • Because P is needed in large quantities during the early stages of cell division, the initial overall symptom is slow, weak, and stunted growth. • P is relatively mobile in plants and can be transferred to sites of new growth, causing symptoms of dark to blue-green coloration to appear on older leaves of some plants. Under severe deficiency, purpling of leaves and stems may appear. • Lack of P can cause delayed maturity and poor seed and fruit development.

28. Potassium : functions • K assists in regulating the plant’s use of water by controlling the opening and closing of leaf stomates, where water is released to cool the plant. • In photosynthesis, K has the role of maintaining the balance of electrical charges at the site of ATP production. • K promotes the translocation of photosythates (sugars) for plant growth or storage in fruits or roots. • Through its role assisting ATP production, K is involved in protein synthesis. • K has been shown to improve disease resistance in plants, improve the size of grains and seeds, and improve the quality of fruits and vegetables.

29. Deficiency symptoms • The most common symptom is chlorosis along the edges of leaves (leaf margin scorching). This occurs first in older leaves, because K is very mobile in the plant. • Because K is needed in photosynthesis and the synthesis of proteins, plants lacking K will have slow and stunted growth. • In some crops, stems are weak and lodging is common if K is deficient. • The size of seeds and fruits and the quantity of their production is reduced.